Within the fracturing fluid industry, guar based fluids or borate crosslinked guar fluids have historically been used. The use of borate crosslinked fluid is established in the fracturing fluid industry due to its reliability, economics, ease of use, and predictability for crosslinked frac fluid.
Guar is a galactomannan polysaccharide. It is known that the crosslinking mechanism of guar based fluid with borate crosslinker is via the cis-diol functional group possessed by the mannose and galactose moieties of guar.
Other fracturing fluids used in the industry such as carboxymethyl cellulose (CMC) or carboxymethyl hydroxyethyl cellulose (CMHEC) are cellulose derivatives. These polymers do not possess the cis-diol functional group either on their polymer backbone or on derivatives thereof. These polymers are typically crosslinked with transition or main group metals such as Al, Mg, Zr, Ti, Cu, Mo, or Co to generate the crosslinked fluid network. However the polymers currently use metallic crosslinkers which lack the rehealability as a desirable characteristic that borate crosslinked fluids possess.
By providing methods to synthesize new cellulose based polymers that are able to crosslink with borate crosslinker, the present invention offers cellulose derivative polymers that can gain the rehealability characteristic, coupled with great clean-up ability.